In the title compound, C(20)H(21)NO(3), the heterocyclic six-membered ring adopts a half-chair conformation and the pyrrolidine ring adopts an envelope conformation. The mol-ecular conformation is stabilized by C-H⋯O and C-H⋯N inter-actions.

The title compound, C(20)H(24)O(5), isolated from Rabdosia var. lophanthoides Hara, is built up from six fused rings. Cyclo-hexane ring A adopts a chair conformation, ring B exists in a screw-boat conformation and ring C adopts a boat conformation; the three five-membered rings D, E and F adopt envelope conformations.

Nuclear Overhauser difference spectroscopy and variable temperature studies of the 9beta,19-cyclopropyl sterols 24,25-dehydropollinastanol (4,4-desmethyl-5alpha-cycloart-24-en-3beta-ol) and cyclolaudenol [(24S)-24-methyl-5alpha-cycloart-25(27)-en-3beta-ol] have shown the solution conformation of the B/C rings to be twist-chair/twist-boat rather than boat/chair as suggested in the literature. Th...

The asymmetric unit of the title compound, C(23)H(22)N(2)O(2), contains two independent mol-ecules, A and B. The cyclo-hexane ring of mol-ecule B is disordered, with occupancies for the major and minor conformers of 0.570 (9) and 0.430 (9), respectively. The cyclo-hexane ring adopts a boat conformation in mol-ecule A and in the major conformer of mol-ecule B, and a chair conformation in the min...

Seven new cyclic natural polysulfides 1-7 were identified in extracts of two bacterial Cytophaga strains (CFB-phylum) isolated from biofilms from the North Sea. Their structures are based on mono- and dimeric-cyclization products of 2-methylpropane-1,2-dithiol 8, which was also present in the extract in trace amounts. The structures were deduced by analysis of their mass spectra and confirmed b...

The Saccharomyces cerevisiae ERG7(Phe699) mutants produced one chair-chair-chair (C-C-C) and two chair-boat-chair (C-B-C) truncated tricyclic compounds, one tetracyclic 17alpha-exocyclic unrearranged intermediate, and two 17beta-exocyclic truncated rearranged intermediates. These results provided direct evidence for the importance of the residue in affecting mechanistic transitions between C-B-...

The mol-ecule of the title compound, C(23)H(34)O(6), is built up from three fused carbocycles, one five-membered, one six-membered and one seven-membered. The five-membered ring has an envelope conformation, whereas the six-membered ring has a perfect chair conformation and the seven-membered ring has a boat conformation. Intra-molecular C-H⋯O hydrogen bonds together with van der Waals inter-ac...

The title compound, C(15)H(18)O(3), was isolated from Lacta-rius piperatus (Fr.) S. F. Gary collected from the Kunming area in Yunnan province, China. The central cyclo-hexyl ring adopts a chair conformation, while the furan-one ring is close to planar (r.m.s. deviation = 0.0174 Å). The remaining methyl-ene cyclo-hexene ring has a flattened chair conformation. In the crystal, mol-ecules are lin...

The title compound, C(15)H(20)O(5) (systematic name: 5-hydroxy-1a,4a-dimethyl-7-methyleneperhydrodioxireno[5,6:9,10]cyclo-deca[1,2-b]furan-8-one), was obtained by the reaction of 3-chloro-perbenzoic acid with 9β-hy-droxy-parthenolide. The five-membered ring adopts a twist conformation, whereas the ten-membered ring displays an approximate chair-chair conformation. In the crystal structure, mol-...

In the title compound, C(23)H(30)N(2)O(4)·C(2)H(6)O, the indole derivative has four fused rings, forming an indolo[2-3a]quinolizine system, in which one six-membered ring is directly connected to the indole unit and has a distorted chair conformation. The fourth ring is also a six-membered ring, depicting a regular chair conformation. In the crystal, the mol-ecules are linked by N-H⋯O and O-H⋯N...